The electronic device fabrication industry requires various chemicals as raw materials or precursors to fabricate integrated circuits and other electronic devices. Deposition processes such as, chemical vapor deposition (CVD) and atomic layer deposition (ALD) processes, are used in one or more steps during the manufacture of a semiconductor device to form one or more films or coatings on the surface of a substrate. In a typical CVD or ALD process, a precursor source that may be in a solid and/or liquid phase is conveyed to a reaction chamber having one of more substrates contained therein where the precursor reacts under certain conditions such as temperature or pressure to form the coating or film on the substrate surface.
There are several accepted technologies to supply a precursor vapor to a processing chamber. One process supplies the liquid precursor to a processing chamber in a liquid form with the flow rate controlled by a liquid mass flow controller (LMFC) and then the precursor is evaporated by a vaporizer at the point of use. A second process involves a liquid precursor being evaporated by heating and the resulting vapor is supplied to a chamber with the flow rate controlled by a mass flow controller (MFC). A third process involves bubbling a carrier gas upwardly through the liquid precursor. A fourth process involves enabling the carrier gas to flow over the surface of the precursor contained in a canister and carrying precursor vapor out of the canister and subsequently to the process tool. This fourth process, the delivery of chemical vapor from a solid precursor by sublimation, is the subject matter of the present invention.
One challenge associated with conventional vessels that deliver chemical vapor from a solid precursor by sublimation is a difficulty in obtaining high utilization of precursor. In other words—to minimize the amount of precursor left in the vessel when it is taken out of service to be cleaned and refilled. One cause of this problem is that, in conventional solid source vessels, the distance between the surface of the precursor and the inlet and outlets used to circulate the carrier gas, as well as the volume of the area in which the carrier gas contacts the precursor vapor, increases as the precursor is exhausted.
Attempts have been made to increase precursor utilization, including more uniform heating of the precursor chamber and improved carrier gas circulation. Although these efforts have resulted in improvements in precursor utilization, the structures needed to implement these improvements can make the vessels more difficult to clean and there is a need for further improvement in the precursor utilization.